The present invention relates to a process for treating the periphery of an unexposed photosensitive resin plate. More specifically, the present invention relates to a process for removing the stickiness of the periphery of an unexposed photosensitive resin plate.
While the production of printing plates from photosensitive resin plates generally includes steps of exposing, washing out, drying, post-exposing, etc, a step for handling unexposed photosensitive resin plates exists before the exposing step. The said step for handling unexposed plates means taking out unexposed plates from packing cases, cutting them according to the size of negative film, printing images on an exposing table, and so on. In the presence of stickiness on the periphery of unexposed plates, the smooth processing of these steps will be prevented, giving rise to inconveniences in handling. The periphery here means the sides of an unexposed plate and is resin surfaces externally bare. For example, the periphery of an unexposed plate sticks to a package or cushion sheet during its removal from a packing case, the periphery of an unexposed plate sticks to a cutting table while the plate is being cut, and the periphery of an unexposed plate sticks to an exposing table or vacuum adhesion sheet during exposing. In addition, problems such as dust deposition on the periphery of unexposed plates, and stickiness of unexposed resin to hands during handling of plates occur, for which reasons a process for removing the stickiness of the periphery of an unexposed plate is desired.
In order to solve these problems, there have been proposed methods including a method in which an inorganic powder is deposited on the periphery of an unexposed plate to remove the surface stickiness, a method in which the periphery of an unexposed plate is covered with a non-adhesive sheet such as release paper, and so on. Of those, the method in which an inorganic powder is deposited on the periphery of an unexposed plate to prevent the stickiness of the surfaces requires a complicated manipulation of the steps for the deposit of the powder, and is of no practical use since it may produce unsatisfactory image quality in the steps of making printing plates, such as exposing, because of the powder deposited on the surfaces of the plate; and the method in which the periphery of an unexposed plate is covered with a non-adhesive sheet such as release paper is of no practical use either, since even if the method could prevent the peripheral resin of the unexposed plate from sticking to the package or cushion sheet, the peripheral resin of the unexposed plate can stick to an exposing table, vacuum adhesion sheet, and to hands during the exposing step.
When the photosensitive resin composition is a photosensitive elastomer containing a conjugated diene polymer, there is practically no appropriate methods in the conventional methods, since the resin of such composition is softer and stronger in stickiness. Accordingly, the present invention aims at developing an easy and effectively practical process for removing the stickiness of the peripheral resin of an unexposed photosensitive resin plate, which causes no problem during making printing plates.